Apparatus for palletizing bundles of newspaper is known in the art. A conventional palletizer for boxes or cartons may use a horizontally, reciprocally movable stripper plate for carrying boxes to a position above a pallet onto which the boxes are to be loaded. The stripper plate is then withdrawn from beneath the boxes, thereby depositing them onto the pallet. A retainer is used for preventing the boxes from moving with the stripper plate as it is withdrawn. Such retainers commonly include a bar which abuts the side of the boxes facing the direction of stripper plate withdrawal. Structures of this general nature are disclosed in, for example, U.S. Pat. No. 3,149,732 Gagnon et al and U.S. Pat. No. 3,833,132 Alduk.
U.S. Pat. No. 4,704,060 discloses a palletizer for palletizing stacks of loose materials such as newspapers, signatures, sheets of paper, and the like. The '060 patent discloses a transfer plate assembly and plate mover, for depositing material onto a pallet or onto a partial load of material on a pallet. In that teaching, underlying compressible materials can be compressed by the transfer plate assembly during the process of depositing the material. Both the material being deposited and the underlying material can be prevented from moving with the transfer plate assembly, by first and second sets of fingers projecting into channels in the top and bottom surfaces of the transfer plate assembly. The pallet load which results from loading a pallet as disclosed therein consists of a plurality of stacks of loose material extending from the underlying pallet, or a slip sheet thereon, to the upper extremity of the stack, typically the top of the pallet load.
Within that environment of continuous stacks, unloading the material from the pallet is typically done by manual labor. In that process, the material is removed in a series of steps limited by the amount of material a person can manually lift at one time.
Alternatively, unloading might be done by a depalletizer wherein essentially an entire layer of the material is pushed, or swept, off the pallet at one time. The latter case of using a depalletizer is preferred in that it reduces the chance of back injury caused by excessive manual labor at the point of depalletizing, along with the associated savings in labor costs.
One problem with moving loose stacks of materials automatically is that each unit of material on the pallet must be acted upon in some way, by the apparatus, to affect the desired movement.
A unit of material is herein defined as any article, or group of articles, of the load, requiring a separate external force to cause it to move. Thus a single loose sheet of paper is a unit as is a bound bundle of papers. For assembled documents, such as newspaper, each document is generally a unit of material.
With the small thickness of, for example, paper, it is easy for sheets, near the bottom of a stack, to be missed by typical material handling apparatus which functions by action on a side of the stack or unit of material as a whole, at the edges of the sheets. Yet, efficient material handling of thin sheets typically is done through interactions at the sheet edges.
Another problem with automatically moving stacks of thin-section materials is moving the stacks or units of materials from an in-feed conveyor or the like, into the palletizing apparatus. U.S. Pat. Nos. 4,704,060 and 4,988,264 address methods of moving thin-section material, wherein the thin-section material is positioned on a transfer plate assembly, or on a spacing sheet on a pallet. In both such cases, the transfer plate assembly or spacing sheet can be precisely positioned, such that channels in the upper surface of the transfer plate assembly or sheet are correspondingly precisely positioned. Further, in those teachings, the channels extended at a uniform depth along the entire path of movement of the units/stacks of material. Thus, it was expedient there to mount a push arm above the transfer plate assembly or sheet such that fingers on the push arm were precisely aligned and thus extended into, but did not touch the walls of, the channels. Accordingly, the fingers could reach below the top surface of the transfer plate assembly or sheet and sweep off even thin-section sheets and the like at the plate/sheet surface.
In addition to the above mentioned patents, palletizing apparatus is disclosed in the following United States patents, the following patents also being disclosed in U.S. Pat. No. 4,704,060.
______________________________________ Locke et al. 2,875,907 Woodcock 2,875,908 Keyes 2,878,948 Gagnon 3,149,732 Jeremiah 3,166,203 Kampert 3,257,006 Grasvoll 3,594,977 Larson 3,606,310 Brockmuller et al. 3,637,093 Grasvoll 3,648,857 Carlson 3,669,282 Alduk 3,833,132 Golantsev 3,837,140 Kelley 4,030,618 Schmitt 4,162,016 Schmitt 4,195,959 Pantin et al. 4,205,934 Faltin 4,230,311 Donnelly 4,234,280 Meratti et al. 4,255,074 Cox et al. 4,342,531 Sylvander 4,383,788 Werkheiser 4,422,549 Werkheiser 4,439,084 Wise 4,477,067 ______________________________________
In this teaching, we address pushing the same types of materials from the in-feed conveyor or the like, onto the in-feed station of the palletizer. The in-feed station of the palletizer has a receiving plate for receiving units of material from the in-feed conveyor. The receiving plate can be a transfer plate assembly that ultimately moves, with the material on it, to another station in the palletizing operation; or it can be a stationary plate that receives and holds the units of material while a layer is being formed thereon, and then gives up the formed layer to the transfer plate assembly.
As the push arm pushes thin section material off the in-feed conveyor, and onto the receiving plate, it must reach below the tops of the carrying elements which carry the units of material on the conveyor, in order to assuredly remove all the material from the conveyor.
Pushing thin-section material across the in-feed conveyor presents two new constraints. First, as the push arm sweeps transversely across the in-feed conveyor, it passes over the conveyor carrying elements while reaching below the tops of the carrying elements, and into the intervening spaces. The spaces between the carrying elements of the conveyor present a first depth into which the push arm must reach. The channels in the receiving plate present a second, typically different, depth into which the push arm must reach. These two depths typically are different, and present the problem of how to assuredly sweep the material from both depths on a single sweep of the push arm.
Second, the "fingers" of the push arm must reach into both the spaces between the carrying elements in the conveyor (a type of channel, and referred to hereinafter interchangeably as both channels and spaces), and into any channels in the receiving plate. This suggests aligning the "fingers" of the push arm with both the channels in the conveyor and the channels, if any, in the receiving plate.
The first constraint suggests limits on the depth to which the fingers can reach into the channels, typically controlled by the height of the top of the conveyor frame. The second constraint suggests aligning the spaces (or channels) between the carrying elements of the in-feed conveyor with the channels in the receiving plate, so that a single set of fingers on the push arm can be aligned with the "channels" in the conveyor, and also aligned with channels in the receiving plate. In such an arrangement, each channel is assigned to receive a particular finger, and each finger is assigned to a particular channel, before the material handling operation begins; whereby the coordination of specific finger/channel pairs is pre-arranged, and generally remains constant throughout the use life of the material handling apparatus.
While the above-suggested alignment may be possible, it adds undesirable complexity to the control of the in-feed system.
It is an object of this invention to provide a push arm which obviates the two above constraints, without adding the suggested undesirable complexity of control.
Thus, it is an object to provide material handling apparatus wherein the depth to which the fingers can reach is not limited by the conveyor frame, or by the receiving plate.
It is a further object to provide material handling apparatus wherein channels on the in-feed conveyor need not be aligned with channels on the receiving plate.
It is yet another object to provide material handling apparatus wherein brush bristles (replacing the conventional fingers) extend into channels on the conveyor to a depth below the top surface of the receiving plate, and effectively sweep the units of material onto and across the receiving plate without any necessity to align the channels in the conveyor with channels in the receiving plate while the material handling apparatus is in operation.